中文摘要：

本文采用可控氮势的多段短时渗氮工艺来制备具有均匀氮浓度分布的γ-Fe[N]含氮奥氏体薄片试样。通过改变不同时段的渗氮时间和氮势，可以有效控制渗氮层的组织分布。通过SEM观察了其回火组织形貌变化。晶界处分解产物的形貌类似上贝氏体组织的层片结构。晶粒内部的γ＇-FeN和α-Fe的混合组织十分细小致密，具有很高的硬度（〉800HV）。

英文摘要：

The thin foils of γ-Fe[N] have been prepared by a multi-stage gas nitriding process in a quartz furnace with the expected nitrogen concentration distribution. By adjusting the nitriding time and nitrogen potential in the different stages, the anticipated microstructures are attained distributing along the nitrogen atoms diffusional direction. The OM and SEM observations show that the decomposition products on the primary austenite grain boundaries have the lamellar microstructure same as the upper bainite. The mixture of γ-Fe4N and α-Fe inside the austenite grains was detected with high microhardness more than 800HV by reason of their nano-scale microstructure.